IS 9452 ( Part 1 ) : 1993 ( Reaffirmed 2004 ) MEASUREMENT OF SEEPAGE LOSSES FROM CANALS - CODE OF PRACTICE PART 1 PONDING ( METHOD First Revision ) UDC 626'82 : 624'131.64 : 532'57 : 006'76 @ BIS 1993 BUREAU MANAK September 1993 OF BHAVAN, INDIAN STANDARDS ZAFAR MARG Price Grarar 3 9 BAHADUR SHAH NEW DELHI 110002 Irrigation Canals and Canal Linings Sectional Committee, RVD 13 FOREWORD This Indian Standard ( First Revision ) was adopted the draft finalized by the Irrigation Canals and Canal approved by the River Valley Division Council. by the Bureau of Indinn Standards, Linings Sectional Committee had after been operation and maintenance, and canal lining research and development Irrigation project design, req;ire accurate and economical measurement of seeprge rates. The possible bencfils from canal lining are saving in water, elimination of waterlogging, and reduction in maintc.rancc cost. Hence, correct assessment of seepage losses from unlined canals and field observations arc the best means to make a realistic assessmcr,t. The loss of water by seepage from unlined canals in India generally varie? from 0.3 to 7'0 m3/S/106 mz depending on the permeability of soil through which the canal p:~sses, iocation of water tables, distance of drainage, bed width, side slope and water depth inside tl:c canal 111 addition, fow velccity. soil and water temperature, atmospheric pressure and stratification c;f the underlying soil also affect the seepage rate. The seepage losses from unlined canals can be calculated by analytical methods or dctz:-mined by direct measurement. The analytical calculations of seepage losses based on cocflicicnt of'h~~dr:.~lic couductivlty of soil and the boundary conditions of the flow system, are of particuinr value for the canals which are in the planning stzgc. The methods of direct measul-en;cut cf'szep,~gc are applicable to the existing canals. Ccrrently accepted ructhcds for direct measurement of seepaFc losses f>orn cxic5tirT; c:ln;rIs :"e pcndicg, inflow-cyutflow and seepage meter mc!hods. In addditiol), there are : p. CIA n~~`lI;i)+.lS SUCII nb tracer tcchniquc, electrical lo~,nin.~ cr resistivity rncasurcmcnt, picz!>rnitric :.::I \ci J,:. ;I,::I~ The ponciir-g and inflow-outflow methods arc applicable re~,arJl~.tr; UT c:in;ti (3.1 remote sensing. The sccpnge meter cannot be used where the canal l;a~ a rcc!;y bcttom (:I IIC:~VY soil condirions. weed growth. The tracer tecllnique is best sullcd to canals in honloE::?: ratio Bed Width/Depth of Water BID up to 5 5 to 20 Exceeding 20 1 IS 9452 ( Part 1 ) : 1993 5 CONSTRUCTING THE PONDED SECTION 5.1 Three methods or combinations thereof may be used to create the ponded section; which of these is used depends primarily on the size of the canal. 5.1.1 The first method comprises construction of temporary barrier or bunds built of canvas held in place by a timber at the top and dirt thrown Such a along the edge on the cross-section. dam is normally restricted to small canals where the water table is less than about 0'6 m above canal bed. A heavy weight canvas treated with water proofing will usually function with a Heavy plastic sheets may minimum of leakage. also be used. 5.1.2 In the second method, the pond may be constructed with earthen bunds at each ecd. The material is usually pushed into place with the help of a dozer or some other device. If the canal is dry, during bund construction the dozer can compact the soil by repeated trips back and forth across shallow lifts. When the canal contains water, care should be taken not to attempt compaction until the movement of water past the bund has been stopped and the base width is sufficient to resist unrestricted spreading of the fill from the weight of the dozer. Natural soil moisture is usually sufficient to attain reasonable compaction. The bund should be made impervious by laying low density polyethylene ( LDPE ) film. The thickness of LDPE film should depend on the initial ponded water depth as given below: Water Depth to be Ponded Thickness of LDPE Film ( Micron ) Water Front spdof u 1'5 : I 2: 1 2: 1 Up to 1 m lmto2m Exceeding 2 m 100 150 200 5.1.3 Soil cover of 15 cm to 30 cm should be provided over LDPE film to protect the film from damage. 5.1.4 A typical set up for observing seepage losses by ponding method is given in Fig. 1 and 2. 5.1.5 In the third method, existing structures such as regulators may be used to pond water. Planks may be used and placed in the stoplog slots. Canvas may be draped over the ponded side to cover open joints and to prevent leakage around the ends of the planks. The canvas is held in place along the edges and ST!LLING `NELL -l FIG. 1 TYPICAL PONDING METHOD SETUP FOR SEEPAGE LO§SES - POIIITER' HOOK GAUGE FIG. 2 TYPICAL CROSS SECTION OF PONDING METHOD SETUP FOR SMALL CHANNELS IS 9152 ( Part 1 ) : 1993 bottom by soil packed against it. may be substituted for canvas to joints. 6 EQUIPMENT LDPE film cover the operative. measurement of the rate of drop in the water surface may be started. The observations of the tests should be recorded in the proforma as given in Annex A. The time of each reading should be recorded to the nearest minute. 7.3 For smaller channels 2 m the arrangement up 6.1 The equipment required to cocduct ponding tests is simple to operate but adequate precautions have to be taken when installing it. 6.1.1 The equipment consists of two hooks/ pointers and two staff gauges and in some locaticns an evaporation pan. A hook and staff gauge should be paired for use at the upstream and dow;lstream ends of the pond. The hook gauge is a laboratory type gauge and can be read up to 0'0001 III with the aid of the vernier. The staff gauge is a standard enamelled gauge frequently used on irrigation projects to indicate the water depth and scaled to 0'001 m ( see ) IS 4080 : 1967 ). 6.1.2 The gauges should be installed on vertical uprights that have been firmly positioned Each gauge should near the edge of the pond. be connected to survey bench marks on the canal so that depths in the pond can be correlated with design depth. 6.1.3 Two sets of hook and staff gauges should should be used. The staff gauge reading serve as a rough check of the hook gauge reading and should the hook gauge be accidentally disturbed, the staff gauge should be read until resurvey establishes a new reference on the hook. 6.1.41 During windstorms, the water surface of the pond may not be horizontal throughout the length of the pond. Therefore, average water surface elevations should be determined by having gauge readings at each end. A stilling well should be provided around the hook to minimize the error in observations due to disturbances in the water surface. 6.1.5 Evaporation Pan The evaporation losses from the pond surface may b:: significant as compared to seepage 1osi;es from lined canals. In order to apply corrections due to evaporation, an evaporation pan should be used for measuring the evaporation rate during the pondng tests. To determine may be made to evaporation, a reference IS 6939 : 1992. 7 PROCEDURE 7.1 Gravity flow or pumping may fill the test pond depending on the that prevail at the site and the size of The filled up water should be free silt content. 7.2 With the pond filled and shown to a bed width of in Fig. 2 should be adopted and for wider channels stilling wells located at extreme ends of pond should be constructed intervals. to observe water levels at various 7.4 Before starting the observations for seepage initial reading of the pointer gauge losses, should be taken on each stilling well s:multaneously and recorded. 7.5 The rate of fall of the water surface within a few hours after the initial readings of the gauge should provide an indication of loss rate. If the pond seems to have a high loss rate, reading should be recorded at an interval varying from 1 to 4 hours, for a pond showing a very slow rate of drop, less frequent readings may be taken. Seepage losses may be computed from the observations recorded after- the steady state condition has been achieved. 7.6 Observations should rainfall or else rain-gauge 8 ANALYSIS be avoided during should be installed. OF RESULTS 8.1 Survey notes should be used to compute and tabulate the water surface width and wetted perimeter for various water surface elevations of canal as shown in Annexes B and C.The cross- section of the canal should be plotted accurately to obtain wetted perimeters and water surface width, correct up to 0'01 m. The increments of elevations for compuations of water surface widths and wetted perimeter depend upon the size of the canal, depth in the pond and the range of the test depths. Each column under a particular elevation is averaged for all stations. to obtain the representative characteristics for the entire pond. info:mation contained in Annexes A, B and C is sufficient for computation of loss rates. To facilitate these computations a statement as shown in Annex D should be prepared. 8.2 The 8.3 Seepage rate ( m9/S/106 m2 ) under steady state condition is obtained by the formula: Total volume lost ( rn" ) x 10R Seepage rate = -~ -~-~~~ 3 600 X average wetted perr[ mS/S/105 m2 ] meter ( m ) X Total time in hours x length of pond ( m ) be used to conditions the canal. from high gauges 3 9 LIMITATIONS 9.1 Ponding all method has the following IS 9452 ( Part iimitations 1 j :1993 and disadvantages: the normal working 4 4 The method interrupts of the canal; of temporary barriers b) The construction or bunds to form the pool and their removal afterwards will involve expense. The method shou!d, therefore, be employed only when the importance of the test warrents the expenditure; of water is n-_eded for Cl A large quantity filling the pool initially and subsequent replenishment during the test may involve difficulties; ,4 Although the ponding method gives accurate figl!res for the total seepage losses from the pool, it does not show variaticn in rates for different paris of the paol; The seepage losses for the pool may be slightly different from those taking place from the canal with flowing water. However, the difference would be quite inconsequential; In the computation of seepage losses, it has been assumed that the effect of va,riable head is negligible; and f) g) The losses worked out are the losses in the tolal experimental reach for the water table, temperature and humidity conditions in the reach at the time of the experiment. 10 ADVANTAGES The method dependable. is relatively more accurate :Bnd ANNEX A ( Clause 7.2 ) SEEPAGE Canal ,.............. Distributaries Other Date Hook gluge LOSS DATA PQNDPNG METHOD end... .., . . . . One end . . . . . . . . I . . . . ..othcr . . . . . . . . . . . . . . . . . . . . . . . . . . . . . StaR gauge .. . ._ . . . . . . . . . . . . . . . . . . . . . . . . . . .. __~ --_-I Staff Gauges r__--h---_-) Other One End . . . . . . . . . . . . . . . . . ..Chainage... One end . . .,. . . . . . . . . . . . . . . . + end . . . . . . . . . . . . . . .,. . . . . . . Observer Time __I-~-.-__. l_l_____-____-_--_ Hook Gauges (.------h-___~ One End Other End End --___. .._ Tcmperaturc r-_-h_write? Air 4 IS 9452 ( Part 1) : 1993 ANNEX B ( Clauses 8.1 and 8.2 ) TABLE OF WATER SURFACE WIDTHS Name of canal .. . . . . . . . . . . . . . . . . . . . . . . Chainage ..a...* . . . . . . . . . . . . . . s.. . . . . . . . . . Cbainage KM Water Surface Width for Various Elevations ~--------h_----_--~ El . . . ..,..... . ..El . . . . . . . . . . . . . . El . . . . . . . . . . . . . . . Pond No . . . . . . . . . . . . . . . . . . . . . . . . . . . . Average ANNEX C ( Clauses 8.1 and 8.2 ) TABLE OF WETTED PERIMETERS Name of canal . . . . . . . . . ." . . . . . . . . . . . . Chainage KM Pond No . . . . ..(........................ Wetted Perimeter for Various Elevations h_____-_-7 r-------El . . . . . . . . . . . . El . . . . . . . . . . . . El . . . . . . . . . . . .El . . . .. . Average IS 9452 ( Part 1 ) : 1993 ANNEX D ( Clause 8.2 ) STATEMENT SHOWING THE DETAILS FOR COMPUTING LOSSES BY PONDING METHOD Water Sllrface Elevation Evaporation Correction ( m ) Rainfall Correction ( m ) Corrected Water Surface Elevation (m) 7 Water Volume SurLost face ( m9 ) Width ( m ) SEEPAGE Date Time Accumulated Time (b) Wetted Average PeriWetted meter Perimeter (m) (m) Seepage Rate cumec/ rn0 1 2 3 4 5 6 8 9 10 11 12 6 Standard Mark The use of the Standard Mark is governed by the provisions of the Bureau of Indian Act, 1986 and the Rules and Regulations made thereunder. 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